The invention relates to an unwinding apparatus for paper or board web rolls or the like integrated with a succeeding rewind station, such as a two drum winder, a single drum winder, or the like.
Such an unwinding apparatus is known from U.S. Pat. No. 3,327,959. On it, an expiring winding roll (empty spool) is exchanged for a new, full roll (parent roll) while the web is being pulled off the winding roll at reduced speed. In the process the expiring roll is lifted out of the unwinding position and the new parent roll is conveyed out of its waiting position into the unwinding position. The web continuing to be unwound from the roll in the new position is led around a guide roll, which extends close along the periphery of the new parent roll in the unwinding position. The new web beginning on the parent roll is given an application of adhesive to attach the beginning of the web to the expiring web of the empty spool. For this purpose the peripheral speed of the parent roll must be matched to that of the unwinding web. Shortly before the web material on the spool has been completely unwound, the guide roll is swung against the periphery of the new, rotating parent roll in order to being the end of the unwound web in contact with the splicing point of the parent roll. When the splice has been made, a separating device separates the expiring web, which carries the beginning of the web along onto the new parent roll. The empty spool is now lifted out of its position and deposited in a storage means out of which it can be taken with a hoist.
To be capable of performing such an exchange of the empty spool for a new parent roll, the known unwinding apparatus is designed relatively expensively: guideways and drive means must be provided to convey the expiring roll out of the unwinding position. The succeeding new parent roll brought into the unwinding position is synchronized by means of a drive with the speed of the unwound web. Furthermore, a sophisticated machine control system is provided to perform the splicing operation. Nevertheless, with the known device, uncontrolled web doublings of differing lengths occur during the splicing operation, which may lead to troubles with the subsequent processing of the web.
In the case of winding machines in which, for example, after a longitudinal slit of the unwound web, the web is wound up on two drums or single drums into rolls which are relatively large in diameter, it is necessary, on completion of these rolls, to stop the machine so that the rolls can be taken out of the machine. Completion of the rolls is arranged in such a way that during such a stop an empty spool can be exchanged for a new parent roll. The time advantage obtained with the aforementioned known unwinding apparatus decreases quite considerably during the exchange of the empty spool for a parent roll.
Furthermore, an unwinding apparatus for continuous operation is known from U.S. Pat. No. 4,443,291, with which the web of a new parent roll located in a waiting position is led by a dancer roller and held with the web-beginning at a stationary cross member of the apparatus with vacuum. The web drawn off an expiring roll is led close to the web-beginning provided with an adhesive tape over two guide rolls which are mounted in swivellable frame. This is equipped between the guide rolls with a separating device for the web as well as with a pressure roll following in the direction of web travel, opposite the cross member. To join the web being drawn off the expiring roll with unreduced speed to the beginning of the web of the new roll, the frame is swung against the beginning of the web located in the waiting position. A knife of the separating device separates the running web, while the pressure roll presses the thus formed web-end against the beginning of the web and joins the two. The running web now accelerates the new roll to the required peripheral speed. Due to this joining technique of a running web to a stationary web-beginning, the unwinding apparatus is suitable either only for relatively low speeds or for winding rolls of small mass.